Clock



FIG. 1 is a perspective view of a clock showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a top view thereof;

FIG. 4 is a rear view thereof; and,

FIG. 5 is a left view thereof.

The broken line showings on the rear of the clock in FIG. 4 are for illustrative purposes only and form no part of the claimed design. 

The ornamental design for a clock, as shown and described. 